What was the reason behind the Second Indian Removal?

The Natives Indian tribes from the Western side required to move to reservations.

Explanation:

Native Indians during the mid-1800s forced to move to the West. The Indian Removal Act by the government of the United States led to the immigration of the Native Indians to the Indian Territory. Tribes from Northern moved to South Dakota, and Southern tribes relocated to Oklahoma. The resettlements of Native Indians created the Second Great Removal.